2.4" Marston Magna Ammonite Cluster

This is a cluster of Promicroceras marstonense ammonite fossils from Marston Magna, Somerset, England. The ammonites are of the species Promicroceras marstonense and are Lower Jurassic (~200 million years old) in age.

Ammonites were predatory mollusks that resembled a squid with a shell. These cephalopods had eyes, tentacles, and spiral shells. They are more closely related to a living octopus, though the shells resemble that of a nautilus. Ammonites appeared in the fossil record about 240 million years ago and they barely survived several major extinction events. The last lineages disappeared 65 million years ago at the end of the Cretaceous.